Surface modification of aluminum foil and PTFE film by graft polymerization for adhesion enhancement

Modification of aluminum foils via surface graft polymerization of glycidyl methacrylate (GMA) to promote their adhesion to the similarly modified pol y(tetrafluoroethylene) (PTFE) films is reported. The properly cleaned surfa ce of the aluminum foil was first silanized with 3-(trimethoxysilyl)-propyl -methacryIate (APS). The silanized Al foil was pretreated with Ar plasma to generate peroxides and hydroperoxides before been subjected to UV-induced graft polymerization of GMA (the AI-APS-g-GMA surface). The Ar plasma-pretr eated PTFE film was similarly modified by W-induced graft copolymerization with GMA (the GMA-g-PTFE surface). The modified aluminum and PTFE surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and atomic for ce microscopy (AFM) measurements. The adhesion between the Al foil and the PTFE film was achieved by introducing a small amount of GMA and hexamethyle nediamine (HMDA) solution mixture or HMDA alone at the lapped interface, fo llowed by curing at elevated temperature. T-peel adhesion strength of simil ar to 13 N cm(-1) was achieved for the Al-APSg-GMA/ GMA+HMDA/GMA-g-PTFE ass embly, compared to only similar to5 N cm(-1) attainable in the correspondin g Al/ GMA+ HMDA/GMA-g-PTFE assembly involving only the pristine Al foil. Si milarly, the use of GMA graft-copolymerizied PTFE film resulted in a signif icant increase in adhesion strength of the Al/PTFE assembly over that obtai ned using only the plasma-treated PTFE him. Cohesive failure in the bulk of the PTFE substrate was observed for the Al-APS-g-GMA/GMA + HMDA/GMA-g-PTFE assembly. (C) 2001 Elsevier Science B.V. All rights reserved.